(a) Technical Field
The present invention relates to a method for preparing a cobalt-based catalyst used for Fischer-Tropsch synthesis.
(b) Background Art
Natural gas has been drawing much attention as an alternative source of energy that can reduce dependency on petroleum. Natural gas is highly evaluated as an alternative to petroleum in that it is distributed relatively uniformly worldwide, its reserves is about 1.6 times that of petroleum with 67 years and it is a clean fuel that hardly produces pollutants such as sulfur and nitrogen compounds. However, natural gas is disadvantageous in that large-scale investment is for pipelines or natural gas liquefying facilities to transport it from production sites to consumers. In addition, in order to ensure economic feasibility, the reserve should be above a certain level and securing of a market is necessary. The gas to liquids (GTL) process is expected to overcome these limitations and facilitate economical utilization of natural gas.
The traditional GTL process converts natural gas to liquid fuels or chemicals via synthesis gas and consists of three major reactions—reforming of natural gas, Fischer-Tropsch (FT) synthesis and cracking of wax in products. In particular, the FT synthesis of preparing liquid hydrocarbons from the synthesis gas is the heart of the GTL process. The FT synthesis allows effective production of various hydrocarbon fuels and highly value-added chemicals from the synthesis gas and is drawing a lot of attention in the energy-related industry. Since the FT synthesis allows production of various types of petroleum products through process improvement or change in reaction conditions including catalysts, production can be varied flexibly depending on market circumstances.
Various catalysts for FT synthesis have been developed up to the present. Their catalytic activity is of great importance since it is directly related to productivity. The catalysts used for the FT synthesis mainly use metals such as palladium, nickel, iron, cobalt, etc. as active component. In particular, iron and cobalt are the active component of commercially available catalysts. Recently, a cobalt-based catalyst including zirconium, titanium, chromium, vanadium or manganese as cocatalyst was developed [International Patent Publication Nos. WO 1997/00231 and WO 1999/34917; European Patent No. 1,042,067]. However, improvement in the catalytic activity can be achieved only when the additionally included cocatalyst metal is closely bound to the cobalt active component.
The inventors of the present invention have studied to develop a method for preparing a cobalt-based catalyst for FT synthesis containing iridium (Ir) wherein cobalt and iridium can be closely bound.